DESCRIPTION (Investigator's abstract): We are testing the hypothesis that a major factor in mammalian aging is the progressive decline in mitochondrial function, resulting from the chronic toxicity of mitochondrially generated oxygen radicals. Mitochondrial oxidative phosphorylation (OXPHOS) is the major source of cellular energy and OXPHOS generates most of the cellular reactive oxygen species (ROS) as a toxic by-product. These ROS damage mitochondrial lipids, proteins, and DNA, impairing mitochondrial function. To determine the importance of mitochondrial ROS toxicity in aging we are studying knockout mice lacking the mitochondrial anti-oxidant enzymes for Manganese superoxide dismutase (MnSOD) and glutathione peroxidase 1 (GPx1). MnSOD -I- animals die soon after birth due to the superoxide inactivation of mitochondrial iron-sulfur center enzymes resulting in dilated cardiomyopathy. The GPx1-/- animals show a mild growth inhibition and reduced OXPHOS efficiency. To further clarify the role of mitochondrial ROS toxicity in aging, we propose to analyze mice with different anti-oxidant enzyme levels. Diminished enzyme activities will be created by MnSOD-/-, MnSOD1+, GPxI-/-, and MnSOD-/+ plus GPx1-/- genotypes, while enhanced enzyme activities will be generated by the adult over expression of MnSOD, MnSOD + GPx 1, and MnSOD + catalase from the ROSA26 locus, following activation using a Cre recombinase switch. Mice with reduced, normal, and increased anti-oxidant enzymes will be assessed for their age-related decline in mitochondrial function, accumulation of somatic mtDNA mutations, changes in mitochondrial gene expression, and altered longevity. The pathologic significance of the age-related somatic mtDNA mutations will be investigated by their recovery through fusion of mouse brain synaptosomes or tissue fibroblast cytoplasts to cultured mouse cells, and their subsequent introduction into the mouse germline through female ES cells. Changes in mitochondrial gene expression will be assessed using our Emory Mitochondrial Gene Chip (Mitochip), and the effect of over expression of anti-oxidant genes on longevity will be evaluated by aging studies.